Pseudomonas aeruginosa is an important nosocomial pathogen and of special concern among cystic fibrosis patients. Adherence to host tissue is one of many factors involved in the progression of infection with this bacterium. Major adherence factors are the protein filaments collectively forming pili which extend from the cell surface. Little is known concerning the production of pili in P. aeruginosa or how this process is regulated. The proposed research will study this area by first isolating and characterizing regulatory mutants which are unable to produce pili. The location of the wild-type gene will be determined by complementation with recombinant plasmids containing P. aeruginosa DNA. These genes will be sequenced and the sequence analyzed. The site of interaction of the gene products with the pilin structural gene will be determined. The specific aims of this project are (1) the isolation of pilin synthesis regulatory mutants, (2) the precise localization of regulatory genes, (3) the characterization of these genes, and (4) the establishment of a site of action of their products.